This is an RCDA application to provide salary support for the candidate's scientific growth in the area of aging, exercise and energy metabolism. The major hypotheses are: (1) decreases in energy intake and expenditure, and increases in body fat and loss of muscle mass are mediated by a reduction in physical activity, and not to an effect of aging; (2) deleterious changes in energy intake, expenditure and body composition are reversible by exercise training, and (3) sympathetic nervous system activity (SNSa) plays an important role in the regulation of these physiological processes. The applicant's immediate goals include: (1) to successfully complete and publish the results of the proposed experiments in respected journals, (2) to establish an independently funded catecholamine laboratory and, (3) to successfully compete for a R01 award. The applicant's long-term objectives are: (1) to understand the mechanism of "muscle wasting" in aging individuals, and the potential role of exercise in reversing this process, (2) to define daily energy requirements in elderly persons varying in health and nutritional status by direct measurement of daily energy expenditure and body composition, and (3) to understand the regulation of SNSa and fat metabolism during submaximal exercise in elderly people. Laboratory techniques to be learned are directly applicable to achieving his long-term objectives. These techniques include: in vivo assessment of triglyceride/fatty acid cycling, skeletal muscle protein synthesis and microneurographic recording of sympathetic action potentials.